All birds, independent of their size, must maintain a power output of 10-25 watts per kilogram of body mass in order to fly by flapping their wings. (a) The Andean giant hummingbird (Patagona gigas) has mass 70 g and flaps its wings 10 times per second while hovering. Estimate the amount of work done by such a hummingbird in each wing beat. (b) A 70-kg athlete can maintain a power output of 1.4 kW for no more than a few seconds; the steady power output of a typical athlete is only SOO W or so. Is it possible for a human-powered aircraft to fly for extended periods by flapping its wings? Explain.